The cliché claims that, in springtime, a young person’s fancy turns to love.

That is, unless they’re gearhead—in which case that attention is more likely focused on busting their car out of the garage and getting it out on the road.

But that’s often when they discover the vehicle’s battery is dead and, even after a quick jumpstart, the battery doesn’t always come back to life.

This calls for a little battery and starter circuit research and maintenance.

Car and truck batteries can be fickle devices—fair-weather friends who are only willing to help when the conditions are perfect.

Also like good friends, they need you to maintain a solid connection. This story is all about how to maintain a rapport with your battery and the starting and charging systems. The bottom line is if you maintain these systems now, they will take care of you when you need them.

(Image/Jeff Smith)

Take a moment to read the attached Definitions section at the bottom of this article, as we’ll be using these terms throughout this story.

Understanding How Vehicle Batteries Work

First let’s cover a little bit of how batteries work.

Batteries are like people, they don’t perform as well in extremes of cold or hot weather. Much like humans, an automotive battery will perform at its best around 80 degrees F. but when the temperature drops to below freezing or surges in excess of 100 degrees F, batteries lose some of their efficiency.

This story will mainly address flooded lead-acid and AGM batteries as they are the most popular. There are now lithium-ion automotive batteries on the market and while powerful and lightweight, they cost a bit more and require their own specific battery chargers.

In any kind of weather, it takes voltage to push and amperage to crank over the starter motor. Car batteries are rated in cold cranking amps (CCA) to indicate how much amperage is available. For big cubic inch engines with high compression, this CCA also works as an indicator as to the power available to crank the engine. This, of course, assumes that the starting system is in good condition. We’ll cover some ways that enthusiasts can easily test both their battery and the starting and charging circuit to ensure that all these systems are up to the task.

The Impact of Seasonal Storage on a Car Battery

Springtime is a great time to initiate this project since the battery has probably been sitting unattended for several months. As an example, we tested the basic lead-acid battery in our ‘65 small-block-powered El Camino that had been unattended all winter in a non-heated garage. The battery tested at 12.25 volts using a typical digital multimeter. Based on our battery voltage chart, you can see that this means our battery was only slightly better than 60 percent charged. This is usually enough to start the car, but we decided to give the battery a nice, slow, low-amperage charge to bring it back up to a full state of charge.

This is a great place to explain how a simple test of open circuit voltage with a voltmeter will tell you quite a bit about battery condition. If a multimeter test displays less than 11 volts, this would indicate that this battery is greatly discharged and may be sulfated. This is a condition where lead sulfate crystals have formed on the active portion of the lead plates and interfere with the chemical process of creating voltage. If these crystals are allowed to grow and harden, this damages the plates and will eventually lead to high internal resistance and a dead battery.

Sulfation occurs when a battery sits unused for long periods of time at low voltage. There are two types of sulfation: soft and hard.

Soft sulfation is generally recently caused and is easier to remove through a specific process employed by the new generation of battery chargers that can break-up this soft sulfation and actually improve the condition of a battery. Hard sulfation is more difficult to remove and leads to eventual battery failure. The common indicator that a battery has suffered sulfation damage is that after charging, it will quickly lose voltage over a short period of time—often just a few hours.

A typical bulk battery charger like this old Die Hard unit (left) charges only at fixed rates of either 2 or 10 amps and offers no safety features to prevent over-charging. Many newer chargers, like the Schumacher unit on the right, are designed to custom charge flooded cell, gel type, and spiral cell batteries since these require different charging techniques. (Image/Jeff Smith)

Testing & Assessing a Vehicle Battery

Each cell in a 12 volt automotive starting battery should produce roughly 2.1 volts per cell and with six cells connected in series a fully charged car battery will produce around 12.6 volts. In the case of the battery we tested at 12.2 volts, this indicated it was at roughly 60 percent charge. With a simple recharge from our Schumacher battery charger set at a low 3 amps brought the battery back up to a full charge reading of 12.6 volts in a couple of hours.

This is the simplest test to determine battery condition. Using a digital voltmeter to read DC battery voltage, the meter on this battery reads 12.16 volts. Referring to the included chart, this indicates barely 50 percent. If we charge the battery and the voltage remains consistent at roughly 12.6 volts then the battery is good. If after charging the battery voltage quickly drops more than 0.20 volt then it may be suffering from high internal resistance or an internal short. It’s best then to have the battery load tested. Most auto parts stores will perform this as a customer service. (Image/Jeff Smith)

After two days, the battery was still at 12.6 volts indicating that it was capable of holding a charge and was not damaged. However, if after several days the voltage had dropped back to 12.2 volts or lower with it merely sitting on the bench, this would indicate a damaged cell that would probably require replacing the battery.

The Schumacher charger will also display battery voltage as well as a percentage of charge. Here it shows this Optima RedTop battery is fully charged at 12.9 volts. (Image/Jeff Smith)

Summit Racing carries several different battery testers that will help with this evaluation. These testers will add a 10 to 15 second load to the battery and then report with a voltage reading. Digital versions use a process to evaluate the battery’s internal resistance and offer a condition report based on this evaluation. A higher voltage reading after the test indicates a healthy battery. Another option is to take your battery to a local auto parts store that will test your battery for you for no cost.

This OTC battery tester is a more compact version of the older Sun Volt-Amp Tester (VAT) machines your grandfather probably used back in the day. This tool places a short duration amperage load on the battery and indicates whether or not it is a good battery. The meter indicates the voltage that would fall into the green, yellow, or red areas. (Image/Summit Racing)

This is a great place to dispel the urban myth about batteries discharging on a concrete floor. If a battery is left unattended for a long period of time, it will slowly discharge—but not because of its proximity to concrete.

If the battery top is dirty, try this simple test. Place two voltmeter probes at opposite ends of the top of the dirty battery but not connected to either terminal. Most often your voltmeter will offer a reading in millivolts (0.001 volt). This indicates a current flow discharge across the top of the battery.

Clean the battery and this voltage will be dramatically reduced. This is one reason why automotive batteries discharge even completely disconnected from the vehicle. Of course, even clean batteries eventually self-discharge, especially in severe cold or hot weather. Using a trickle charger is a great way to maintain the battery voltage and extend its life by maintaining its full charge voltage which also minimizes sulfation.

If an Optima battery is allowed to fully discharge, it will fall below 10.5 open circuit voltage. Most common battery chargers will not work with these batteries because the Optima’s low internal resistance will allow excessive amperage that could damage the battery charger and/or the battery. One trick is to use jumper cables to connect the discharged Optima to a full charged Optima negative-to-negative and positive-to –positive with jumper cables. This will create sufficient voltage in the discharged battery to allow a low, 10 amp charge to slowly bring the discharged battery’s voltage up to where it can accept a charge by itself. (Image/Jeff Smith)

Testing & Assessing a Vehicle’s Charging System

Now that we have a handle on basic battery maintenance, we can move on to testing the starting and charging system. Hard starting problems are often blamed on the battery when the real culprits require more careful examination. Let’s start with the simplest of things by ensuring the battery terminals, posts, and connectors are clean and free of corrosion. We’ve seen examples of dark film on the terminals that doesn’t appear as corrosion but is sufficient to cause resistance and reduce current flow. While it may seem obvious, ensuring the battery connections are free of these simplest forms of corrosion can make a big difference.

We tested the charging system on our small block El Camino with voltage at the battery reading 14.35 volts with the engine running. We also measured the operating voltage at the alternator at 14.62 volts so the charging system only lost 0.27 volt which is good, relatively low number. A good reading at the battery is anything less than a 0.40 to 0.50 volt drop. (Image/Jeff Smith)

One quick test of battery condition is to disable the ignition and monitor battery voltage during cranking. A healthy battery with a 12.4 or higher open circuit voltage should display a loaded voltage during cranking of roughly 11 to 11.5 volts. If the voltage drops much more than 2.0 volts (down to 10.5 for example), this indicates the battery is struggling.

Here we’ve connected our multimeter to read voltage from the negative battery terminal to the ground connection on the engine. Make sure your battery is fully charged for this test. During cranking, the meter will display a small voltage as shown here with 116.8 millivolts (0.117 volt). This is called a voltage drop test and is used to evaluate resistance under load. Without going through the math, if the multimeter reveals a voltage of more than 0.50 volt, the cable or its connections indicate high resistance to current flow. So for this test, we can see the negative cable side of the starting circuit is good. We came up with similar numbers for the positive cable side as well. If the voltage drop had been roughly 0.75 volt we would then look at the condition of the cables or the connections. (Image/Jeff Smith)

Another evaluation of battery condition is to test open circuit voltage after this cranking test. Let’s say the voltage before the test is 12.4 but after 5 seconds of engine cranking the open circuit voltage falls to 12.1 volts and continues to drop, this is a clue that the battery is suspect. If the voltage is stable after the load test, then the battery is probably in good condition.

Poor results from the above cranking test may not necessarily indicate a faulty battery. If this first test reveals an excessive voltage drop during cranking, it would be wise to next perform a voltage drop test on the battery cables. This involves using your multimeter again set on DC volts. Place the red lead on the negative battery terminal with black lead connected to the ground cable bolt on the engine.

Disable the ignition and crank the starter motor. During cranking, the multimeter will display a voltage. If it reads 0.15 volt or less, this is an indication of decent low resistance in the ground cable. If the meter reads 0.16 volt or more, this indicates resistance in the cable or the connection. This same volt drop test should also be performed on the positive battery cable between the battery and the connection on the starter motor.

The quickest way to check for a current draw is to connect the multimeter between the positive battery cable and the positive post. If the meter reads a voltage there is amperage being drained, pushed with this voltage. A higher voltage reading such as this 2.27 volts means a bigger amperage drain. One way to isolate the circuit is to pull fuses until the voltage drops. Make sure to isolate the dome/courtesy light from this test if the door(s) are open as the dome light will pull amperage. In one instance, we discovered a shorted connection to the dome light that was the cause of the battery drain even with the dome light bulb removed! (Image/Jeff Smith)

Often, even brand new inexpensive battery cables can cause a hot start problem that is often blamed on the battery. This is why large, multi-strand copper cable is preferred. In automotive DC starting systems, large diameter battery cables with multiple strands offer the least system resistance, especially when used with copper terminals.

Sometimes starting problems can be traced to an undersized wire feeding current to the pull-in/hold-in engagement side of the solenoid. This is especially true with high performance starter motors that demand high current flow to the solenoid. In some cases, using a high amperage relay kit to connect with the starter solenoid will prevent re-occurring hot start problems where the solenoid just clicks but will not engage the starter motor. 

One condition that enhances battery discharge is when the battery is dirty and/or heavily corroded. The dirt offers a voltage pathway through resistance, causing the battery to self discharge. This multi-meter shows a significant 173 millivolts (0.173 volt) indicating current travel across the top of the battery. After cleaning this battery the voltage dropped to roughly 11 millivolts (0.011 volt). (Image/Jeff Smith)

Many times, recurring low-voltage battery issues can be traced to the vehicle’s charging system. The first check we like to perform is a simple test that is a good indicator of charging system condition. Using a multi-meter set on DC voltage on a running engine, check the voltage at the output terminal on the alternator. Next, with the engine still running, check the voltage at the battery terminals. If the voltage reading at the battery is more than a 0.50 volt lower, this indicates the charging wire from the alternator to the battery is too small or suffers from excessive internal resistance. This is especially a important for high output charging systems.

There’s much more to this story than we can squeeze into this current events adventure, but these few tidbits should cover the major areas of batteries, starter, and charging systems that should reinforce you to pay closer attention to how these systems work and the importance of proper maintenance.


Common Vehicle Battery Terms & Definitions

  • Lead-Acid Battery – This is the most common style of automotive starting battery. Lead plates are immersed in a sulfuric acid solution producing 2.1 to 2.2 volts per cell.
  • Gel Type Battery – This style uses a material mixed with sulfuric acid to create a gel acid to coat the battery plates to create voltage. This technology offers an increase in performance and durability.
  • Spiral-Cell Battery – This is Optima technology that wraps the cells in a spiral configuration using absorbed glass matt (AGM) that is different from gel construction. This AGM process offers improved vibration resistance which is a common cause of battery failure in lead-acid and gel type batteries.
  • Lithium-Ion Battery – This dry cell technology has been used to power small devices like cell phones but is now available in automotive starting batteries. The main advantage is their extreme light weight which can be useful for race cars. The disadvantage of this design is its higher cost and that it requires a specific charger.
  • Open Circuit Voltage (OCV) – this is the voltage measured at the battery terminals with no load on the battery. This is a quick and simple indicator of battery condition. Most flooded, gel, and AGM batteries will indicate maximum charge at 12.6 to 12.8 OCV.
  • Cold Cranking Amps (CCA) – This is the amount of amperage the battery can deliver for 30 seconds at 0 degrees F and not fall below a 7.2 volt state of charge. Higher ratings mean the battery can deliver more amperage at cold temperatures so a battery with 750 CCA has 50 percent more cold cranking capacity than a battery rated at 500 CCA.
  • Reserve Capacity (RC) – This is a specification in minutes of how long the battery can deliver a consistent 25 amps until it reaches full discharge of 10.5 volts. As an example, a full charged battery with a reserve capacity of 100 means it can deliver 25 amps of constant load for 100 minutes before it reaches 10.5 volts.
  • Amp Hour (AH) – This is a similar yet different amp rating usually reserved for deep cycle batteries intended for continuous use such as powering an electric trolling motor for a boat. Most automotive batteries are rated using Reserve Capacity. Amp Hour is the maximum amount of amperage the battery can deliver for one hour at 80 degrees F before reaching full discharge at 10.5 volts. For example, a 55 AH rating would mean this battery could deliver 55 amps continuously for one hour from a full charge until it reached 10.5 volts.


3 Stages of Battery Charging Rate

Modern “smart” battery chargers will automatically shift between Stage 1, 2, and 3 modes. 

  • Bulk Charge (1st Stage) – This is a relatively safe high amperage charge rate that continues until the battery achieves 70 to 80 percent of max charged voltage.
  • Absorption Charge (2nd Stage) – At this stage, voltage remains constant and current (amperage) is tapered down—here is where maximum voltage is achieved—voltage used in this process is usually between 14.2 and 14.7 volts
  • Float Charge (3rd Stage) – This is usually a maintenance charging point with very low amperage that maintains peak voltage. This is the area where “trickle” chargers operate, using a very low (1 to 3 amp) current flow.


Common Domestic Vehicle Battery Groups

Battery DesignationDescription
24Top terminal
24FTerminals opposite 24
27Slightly longer than 24
34Slightly shorter than 24
78Side terminal
34/78Combination top & side terminal


Lead-Acid Battery State of Charge

State of ChargeVoltage
100%12.6 – 12.7 Vdc
90%12.5 Vdc
80%12.4 Vdc
70%12.3 Vdc
60%12.2 Vdc
50%12.0 Vdc
40%11.9 Vdc
30%11.7 Vdc
20%11.5 Vdc
10%11.3 Vdc
0%10.5 Vdc


This Optima red top battery is the main component in this Summit Racing Pro Pack that includes large cables, connectors, and a trick aluminum battery mount. The Optima battery is a 34/78 style with top and side terminals that are great for connecting EFI or electronic transmission controllers that must be connected directly to the battery. The cables included with the kit are high quality 1-0 cables from Painless Performance. The mount can be used to place the battery is a custom location. (Image/Summit Racing)
The key to reducing resistance in the starting circuit is to use large diameter copper cables like these 1/0 Painless cables that come as part of the Summit Racing Pro Pack kit. Multi-strand copper cables are always the best choice for starter motors, especially for high compression engines. (Image/Jeff Smith)
Sometimes you just need a little battery boost when jumping the battery from another car just isn’t available. The battery jump boxes like this Micro-Start unit are lithium-ion battery packs that offer amazing power for their size. We’ve tested this unit at near-zero temperatures with great results. Generally speaking, jumpstart packs like this aren’t expensive and offer a great way to overcome a dead battery. (Image/Summit Racing)
Battery maintainers or trickle chargers like this low-amp unit from Summit Racing offer an inexpensive way to maintain battery life over an extended period of time and are especially useful for cars that sit for long periods of time. These low amperage chargers maintain full voltage and help extend battery life. (Image/Summit Racing)
E3 now offers lithium-ion batteries with sufficient capacity to act as a starting battery. The advantage to these batteries is that they are extremely light yet powerful. A typical Group 24 lead acid battery weighs roughly 40 pounds and offers 700 cold cranking amps (CCA). This E3 lithium weighs only 7 pounds with 600 CCA but is priced roughly four times more than the Group 24 lead-acid battery and requires a dedicated battery charger. (Image/Summit Racing)

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Author: Jeff Smith

Jeff Smith has had a passion for cars since he began working at his grandfather's gas station at the age 10. After graduating from Iowa State University with a journalism degree in 1978, he combined his two passions: cars and writing. Smith began writing for Car Craft magazine in 1979 and became editor in 1984. In 1987, he assumed the role of editor for Hot Rod magazine before returning to his first love of writing technical stories. Since 2003, Jeff has held various positions at Car Craft (including editor), has written books on small block Chevy performance, and even cultivated an impressive collection of 1965 and 1966 Chevelles. Now he serves as a regular contributor to OnAllCylinders.